Clay tennis courts are made up of fine particles including, for instance, crushed meta-basalt stone that has a specification of certain size stone particles that are angular in shape. These angular stone particles seat on each other locking in to give a stable and firm surface. Water is added through different irrigation methods which is essential to this firming action of the surface. Consistent water delivery is important as the clay surface is like a sponge and will absorb the water. Too much water in an area of the court will produce puddling and create a soft spongy surface whereas too little water will create dry hard or unstable areas in the court. A properly watered court surface will keep the surface stable and firm, provide better traction, minimize surface erosion and produce better and more consistent ball bounce.
Court hydration and drying is constant throughout the life of a clay court surface. Weather conditions have to be met with appropriate actions throughout the day. On a hot day, the surface will need to have more hydration as opposed to a cooler day when the surface will need less water. Rain or a thunder storm can provide hydration, but the court can only accept limited amounts of water as most will runoff and drain due to a court's slope which allows the water to drain off leaving some moisture to seep into the clay surface and down through the profile. A healthy clay surface with the right slope angle will absorb an appropriate amount of water while shedding excess water. Too much absorption leaves the court soft and spongy and unplayable until the surface dries out. A clay surface that experiences too little hydration will become unstable or hard which can lockup the surface profile inhibiting water to pass down through it.
Water storage in a clay court is important. There is normally a stone screening base that is able to store water as rain or irrigation occurs. Water will penetrate down through the clay surface profile and be stored within the stone screenings. During the day, capillary action will occur as the sun pulls the moisture up through the surface, keeping the surface moist and hydrated as long as the moisture is in the profile.
Early court hydration systems consisted of an above ground sprinkler system. This type of system is still being used to water clay court surfaces although the number of courts using this system is slowly declining. Above ground irrigation consists of sprinkler heads placed in a specific pattern which allows the water to spray throughout the surface. A good sprinkler system will consist of 8 sprinkler heads. The spray from these sprinkler heads is only as good as the water pressure pushing the spray out to the courts. Too little water pressure does not allow the spray patterns to meet each other causing dry areas around the play area. Too much water pressure can move clay particles around causing an inconsistent surface and can also cause water puddles to occur which can stop play until the puddles have dissipated. Usually there are multiple zones in the system so that water pressure can be controlled by having only 3 or 4 sprinkler heads working at a time. It is rare to have all sprinkler heads operating at one time. Going through this process of each zone coming on is time consuming. Usually a clay court will need hydrating in the mornings before play, in the afternoons and then again in the evenings. Busy facilities do not like to shut down the courts during the afternoon as this costs them an hour or two of court usage.
Above ground irrigation is also not efficient as water waste usually occurs. If not timed correctly, water usage can be a large expense. Water that does not penetrate into the surface will drain off. This excess water is wasted. Another way water is wasted in this system is wind. Wind can push the water spray off of the courts not allowing the consistent water spray pattern that is desired. The goal of watering a clay court surface using an above ground irrigation system is to get the appropriate amount of water down through the profile so that water is stored for the days play as capillary action pulls the water up through the clay surface during the course of the day. It takes time for water to penetrate down through the clay surface using an above ground sprinkler system. This is not an efficient way to hydrate a clay court.
One current clay court sub-irrigation system was designed when irrigation technology consisted of mostly manual controls relying on user experience and knowledge to keep a clay court surface at a desired state. This prior system consists of utilizing gravity to slowly feed the underground cells water that needs to be maintained at a level in the stone screenings that then is wicked up into the fine particle surface layer. Many clay tennis courts are built using some form of sub-surface irrigation, and the number of these courts continues to grow. Prior art sub-irrigation systems operate on a gravity fed water source. A regulation tennis court is 60′×120′. This area is divided into independent water storage cells underneath the clay court surface. There is a matching water control box for each of the cells. These individual operating cells are important as tennis courts have trees and shrubbery surrounding the courts. This allows different environments to occur as you have sun and shade occurring at the same time. More sun means more capillary action which means more hydration needed. Shaded areas need less hydration. Having typically six individual working cells allow users to accommodate for these inconsistent environments on a tennis court. The water control boxes consist of a water source and water level control as well as drainage outlets. Using a float valve borrowed from the toilet industry placed in the control box allows the water level in the control box to be adjustable through a manual process. Adjusting the float device up or down gives the ability to control the water level in the control box. Since this water control box is at the same elevation as the water storage cell underneath the court surface, gravity will slowly balance between the water control box and the cell. This is a time-consuming process and has to be done slowly in order to not flood the cell or the surface. This process changes throughout each season as different water levels are needed in the cells due to seasonal environmental changes. This system has a costly, difficult to install, control system that is slow to react and unintuitive to control or adjust. There is usually a learning curve for the maintenance staff to learn and operate and usually these types of prior art systems are only mastered by experienced users.